Octane measuring

ABSTRACT

Automatic octane measurements are made very rapidly with standard test engine using an all-electronic control that automatically lowers the fuel-air ratio to bring the knock intensity below standard, then automatically adjusts the compression to bring the knock intensity to standard, then intermittently increases the fuel-air ratio, after the first or second intermittent increase permits automatic compensatory compression changes only in the decreasing direction to compensate for departures from standard knock intensity and conducts these compensatory compression changes at a rate too slow for adequate compensation if the fuel-air ratio increase causes a substantial increase in knock intensity, and then indicating the compression ratio reading after the knock intensity remains standard during two to four successive fuel-air ratio increases. Maximum knock fuel-air ratio is indicated by subsequently automatically lowering the fuel-air ratio an amount corresponding to the fuel-air ratio increases during which knock intensity remained at standard. Finally for some purposes the test engine can be permitted to stabilize at the maximum knock fuel-air ratio. Electronic memory can be used to translate compression ratio to octane number, and barometric correction can be made electronically.

This application is a continuation-in-part of application Ser. No.61,473 filed July 27, 1979 (U.S. Pat. No. 4,276,770 granted July 7,1981).

The present invention relates to determining octane ratings.

Among the objects of the present invention is the provision of octanerating determining apparatus and processes which are improvements overprior apparatuses and processes such as those shown in U.S. Pat. Nos.3,383,904, 3,488,168, 3,596,281, 3,614,888, 3,621,341, 3,661,540,3,690,851, 3,913,380, 3,456,492 and 3,949,595.

The foregoing as well as additional objects of the present inventionwill be more fully understood from the following description of severalof its embodiments, reference being made to the accompanying drawingswherein:

FIG. 1 is a block diagram showing the key electrical features of anapparatus exemplifying the present invention;

FIG. 2 is a block diagram of a numerical display arrangement forautomatically displaying octane numbers under the control of theapparatus of FIG. 1;

FIG. 3 is a side view of an attachment for a test engine for use withoctane rating determination;

FIG. 4 is a front view of the attachment of FIG. 3;

FIGS. 3A and 4A are views similar to those of FIGS. 3 and 4, of amodified test engine attachment; and

FIG. 5 is a circuit diagram for an automatic compression correctionpulse generator of the present invention.

The official octane rating system calls for the use of a standard testengine, described for example in the 1977 Annual Book of ASTM Standards,Part 47, published by American Society For Testing and Materials, havinga variabe compression ratio and a knock intensity output signal. Asnoted in the above-numbered prior patents it has been found convenientto place a sample of the fuel to be tested in a bowl of the engine'scarburetor, switch the engine to that fuel, perform an initialcompression ratio adjustment to bring the knock intensity to the desiredstandard, then make a fuel-air ratio search to find the ratio at whichthe fuel produces maximum knock, and make a final compression ratiocorrection to bring the knock intensity to the standard value. Thisentire sequence can be carried out automatically but takes an average ofover 5 minutes, and has required the use of slow-moving mechanicalpeak-picking equipment peculiarly adapted to the idiosyncracies ofstandard test engines.

According to the present invention, the fuel-air ratio search is made byfirst lowering that ratio, adjusting the compression ratio to bring theknock intensity to standard, and finally increading the fuel-air ratioin intermittent steps while permitting automatic compensatory changes ofcompression ratio in the downward direction only and at a correctionrate too slow for adequate compensation if these increases effectsubstantial increases in knock intensity. The entire rating sequence iscompleted when the knock intensity remains at the desired standardduring two to four successive fuel-air ratio increases, without acompression ratio change.

Nothing further need to be done to obtain accurate and highlyreproducible Research Octane ratings and the average time required isless than four minutes, sometimes as low as two minutes. Moreover nomechanical peak-picking is needed so that the equipment can beessentially entirely electronic and highly compact.

The fuel-air ratio will overshoot the desired maximum-knock value,particularly if the intermittent bowl raisings are each about 0.01 ormore inches, so that if the maximum-knock fuel-air ratio is to be alsodetermined, the bowl is lowered at the end of the sequence by an amountcorresponding to some or all of the amount raised after the lastcompression ratio change.

Moreover where the bowl raisings are each greater than 0.01 inch, thefinal compression ratio reached after a Motor Method octane sequence issometimes not reliable unless it will maintain itself for at least about30 seconds. When carrying out a Motor Method sequence it is accordinglyhelpful to keep the equipment operating in 20-second stages after theinitial end-point determination, and preferably after the bowl islowered to compensate for the above-noted overshoot, until nocompression ratio change takes place during such a stage.

Turning now to the drawings, FIG. 1 shows an apparatus that receivessignals at 10 from the knockmeter of a standard test engine, and withthe help of an amplifier 12 the signals are converted inanalog-to-digital converter 14 to a 12-bit digital output. Theknockmeter signals are generally zero to 12 millivolts d.c. analogvoltages corresponding to the intensity at which knocking occurs in thetest engine. These signals are preferably damped by the minimum amountof damping provided in the standard knockmeter, and amplified tozero-to-10-volt d.c. analog signals for delivery to standardanalog-to-digital converters. A set point selector in the form of apotentiometer 16 can be connected to supply a signal level set point,generally a fixed value between 45 and 55 on the zero-to-one-hundredknock intensity scale of the knockmeter. The digital output of theconverter is a binary representation of the knock intensity and isoffset by the set point selector.

That digital output is supplied to a group of detectors 21, 22, 23 and24, and to a knock intensity error generator 30. The output can also besupplied to a logic indicator 20 for displaying the knock intensitysignal as for example for trouble shooting in the event the apparatusmisoperates.

Detector 21 compares the 12-bit signal from the converter with the upperlimit of a dead band width signal received at 41 from a Dead Band WidthSelector 40 that by way of example can select bands corresponding to ±1,±2 or ±3 scale widths on the knockmeter scale. A small dead band, atleast about 1 scale unit wide, is needed to reduce hunting, but widerdead bands enable more rapid though coarser octane ratingdeterminations. It is generally desirable to select a dead band widthcorresponding to the extremes of fluctuation that the test engineundergoes when operating. Detector 21 has two outputs, 33 and 34 whichcarry signals when the 12-bit knock signals correspond to magnitudesbelow or above the upper dead band limit, respectively.

Detector 22 similarly compares the 12-bit knock signals with the deadband width signals and shows at its outputs 36 and 37 whether the knockintensity is below or above the low end of the selected dead band.

Detector 23 compres the knock intensity signals with a pre-determinedminimum known intensity, and delivers at 50 a signal showing that theknock intensity is below that limit. Such a limit can be fixed at 4units below the dead band on the knockmeter scale, or at any other valuedesired for efficiently carrying out the octane determining sequence. Inthe illustrated embodiment the signal at 50 is used to automaticallyterminate the downward movement of the carburetor bowl as describedinfra.

Detector 24 compares the knock intensity signal with a limiting knockintensity setting that should not be exceeded by the test engine.Excessively violent knocking can damage the test engine, and detector 24can be arranged to deliver an out signal at 51 when the knock intensityreaches a value corresponding to 87 or thereabouts on the standardknockmeter scale. Only the signals from the three most significant bitsof the 12-bit knock intensity signals need be supplied to detector 24with such settings.

Generator 30 is supplied not only with the 12-bit knock intensitysignals, but also with the signals from 34 and 36. It compares themeasured knock intensity with the upper and lower limits of the deadband, and puts out an 8-bit digital signal corresponding to themagnitude of the departure of the knock intensity from the dead band.This 8-bit error signal is supplied to a Compression Correction PulseGenerator 28.

Generator 28 also receives the signals from 34 and 36 as well as timingpulses from a timing pulse generator 44. When generator 28 is actuated,it will at each timing pulse produce a compression correcting pulse ofvariable length such as from about 0.1 to about 8 seconds each. Theexact length of the correcting pulse will vary with the magnitude of the8-bit error signal, and will be delivered to an Increase or Decreaseoutput line 47 or 48 depending upon whether generator 28 is receiving abelow-dead-band signal 36 or an above-dead-band signal 34. The Increaseand Decrease signals operate a relay and motor combination 49 such as isgenerally provided in standard test engines to increase or decrease thecompression ratio of the test engine. The minimum correcting pulselength is preferably set at the value that causes the motor to make theminimum change in compression ratio. A manual control 60 for compressionratio changes is also desirable.

A sequencer 70 controls the octane rating determination. It is shown ashaving nine output connections, numbered from zero through 8, and can bea simple ring counter that shifts from one output to the next at eachcounting step. A stepping input is provided at 72, and a reset to zeroprovided at 74. The various outputs are connected to the CompressionCorrection Pulse Generator, to the motor that moves the carburetor bowlup and down, as well as to various timers, as illustrated, with the zerooutput connected to enable the display of octane number.

KNOCK LIMITING OPERATION

With the apparatus connected to a test engine that is running, and withthe control of FIG. 1 energized so that it will operate when needed, nosequencing is taking place and the sequencer output is at the zeroterminal. This keeps an octane display readout enabled so that octanenumbers can be read if for example the equipment is being operatedmanually. No aspect of manual operation is obstructed. The equipment canbe maintained in this standby condition, with the engine operating, sothat it is ready for immediate use to determine octane numbers.

However with no one paying much attention to the equipment, it ispossible for a change of fuel to cause the engine to knock at highintensity, sufficiently high to damage the engine if not promptlycorrected. This high intensity is detected by detector 24 which thenputs out a step signal at 51. The step signal is delivered to step input72 of the sequencer by a circuit that is not illustrated, and shifts thesequencer output to its terminal 1. The octane display is accordinglydisabled, and the Compression Correction Pulse Generator 28 is actuatedthrough line 81. Accordingly the next timing pulse from timing pulsegenerator 44 triggers a Decrease correction signal which is delivered toassembly 49, and the compression change motor is actuated to reduce thecompression ratio of the test engine. This triggering and compressionratio reduction repeats itself so long as the knock intensity exceedsthe upper limit of the dead band, although as the knock intensity islowered toward that dead band limit the correction pulses become shorterin length. The first compression ratio decrease signal responds to avery large knock error and can have a duration so long as to continueuntil the next timing pulse, in which event the motor effectingcompression ratio decrease is continually actuated during the intervalbetween successive timing pulses, or even through three or moresuccessive timing pulses.

When the knock intensity falls sufficiently to enter the dead band, thecompression ratio reduction is automatically terminated. This is shownin FIG. 1 by a resetting of the Sequencer 70. Upper Knock Limit signal51 is illustrated as not only actuating the stepping of the sequencer,but is also connected through lead 62 to set an electronic latch 64 thathas an output line 66. When set there is no signal on that output line.The latch also has a reset input 63 which is actuated by the output of adetector 25 connected to lines 33 and 37 to detect when the knockintensity is within the dead band. When that happens this detectoractuates the reset 63 of latch 64, and since the set input 62 for thatlatch has been deactuated, the latch resets. Upon resetting this latchenergizes its output 66 which is connected to the reset input 74 of thesequencer, and the sequencer is thus caused to reset to its zero output.

The apparatus accordingly safeguards the test engine, and does this evenif the equipment is completely unattended.

AUTOMATIC OCTANE RATING

To conduct an automatic octane rating determination on a fuel when theequipment is in the foregoing standby condition, it is only necessary tohave that fuel supplied from a bowl of the engine's carburetor, and tothen step the Sequencer 70 into its 1-output. For this purpose a manualON switch, not shown, can be momentarily closed to deliver a steppingpulse to stepping input 72. In the 1-output condition the sequenceractivates the Compression Correction Pulse Generator (again through line81) so that the timing pulses from timing pulse generator 44 triggercompression ratio correction pulses if the knock intensity is not in theselected dead band. The first timing pulse after the knock intensityreaches the dead band will cause the Within Dead Band Detector 25 todeliver a step signal from a second output 52 which is supplied to thesequencer stepping input 72. The reset signal 63 which is simultaneouslygenerated by detector 25 does not actuate the sequencer reset inasmuchas the latch 64 is not set.

Sequencer 70 is accordingly stepped to its 2-output. Here theCompression Correction Pulse Generator 28 is actuated through line 82 sothat the automatic compression ratio operation continues to the nexttiming pulse from 44. If at that pulse or at a succeeding pulse, theknock intensity is in the selected dead band, the sequencer stepping isrepeated and the sequecer shifts into its 3-output.

The 3-output actuates generator 28 through line 83, and through a branchline 93 also actuates the down winding 100 of the motor for the testengine's fuel bowl, to lower that bowl. However the actuation ofgenerator 28 by line 83 only permits that generator to deliver decreaseoutput signals.

The downward movement of the fuel bowl reduces the fuel-air ratio of thecombustion mixture supplied to the test engine, and the knock intensitywill diminish. It is possible for the knock intensity to increase beforeit starts to diminish, inasmuch as the bowl might have originally beenat a level that supplied the fuel at a fuel-air ratio higher than itsmaximum knock ratio. The bowl lowering will in such a situation firstbring that ratio through maximum knock. The resulting transient increasein engine knock intensity may trigger a compression decrease signal butwill be otherwise ignored by the apparatus.

Even a transient knock intensity increase to the value that wouldotherwise trigger Upper Knock Limit Detector 24, can be ignored as bydisabling step output 51 of that detector when the sequence is in its3-output stage. Thus output 51 can be supplied through an AND gate thatis only enabled when the Sequencer 70 is in its standby condition andactivating its own zero-output terminal.

Lowering the bowl at the rate of about 4/10 inch per minute providesvery good operation, but other rates from about 1/3 to about 2/3 inchper minute can also be used.

The down movement of the fuel bowl proceeds until the knock intensitydiminishes to the level that triggers Low Bowl Limit Detector 23. Suchtriggering generates a stepping output at 50, which output is suppliedto the stepping input 72 of the sequencer, and the sequencer is thusstepped to its 4-output condition. In this condition the CompressionCorrection Pulse Generator 18 is actuated through line 84. Thisactuation is an unrestricted actuation such as takes places with line 81and 82, and causes the compression ratio of the test engine to beautomatically brought to the point at which the knock intensity is inthe selected dead band. This automatic change amounts to an increase incompression ratio, and if desired can be effected with the generator 28actuated only to deliver Increase signals at its output 47.

The return of the knock intensity to the dead band causes the nexttiming pulse from generator 44 to trigger another stepping signal at theoutput 52 of the Within Dead Band Detector, and this steps the Sequencer70 to its 5-output condition. Here the sequence's 5-output line 85actuates through a timer 95, the up winding 101 of the bowl motor toraise the bowl. The bowl is lifted about 0.10 to about 0.20 inches,preferably 0.15 inches, something easily effected in about 10 to 20seconds, after which timer 95 times out and delivers a stepping signalto an output line 90. This stepping signal is supplied to step input 72of Sequencer 70 and steps it to its 6-output condition.

If the downward bowl movement is prolonged, for example because the LowBowl Limit Detector is set for a very low limit, or because the bowlmotor lowering is so rapid that the test engine's knockmeter output lagsexcessively, the rising of the bowl motor in the 5-output condition canalso be prolonged or can be made in two steps.

In the 6-output condition Sequencer 70 actuates, through output line 86and branch line 96, the intermittent further raising of the fuel bowl.To this end a pulse generator 97 is connected for actuation by line 96,and also connected to deliver its generated pulses to the up winding 101of the bowl motor. These pulses are preferably two seconds long spaced 8seconds apart, but the bowl steps can be from about 0.15 to about 0.05inch each with pauses at least about six seconds long to permit the testengine to stabilize itself after each bowl step. The duration of eachstep can also be reduced to one second or even less if desired, inasmuchas this will speed the octane measurement. Pauses over about 10 secondslong between pulses, unduly delay the measurement.

The 6-output line 86 is also connected to actuate Compression CorrectionPulse Generator to deliver decrease signals only, and in addition anauxiliary line 106 supplied by output line 86 is shown connected toreduce the duration of each Compression Correction pulse while Sequencer70 is in its 6-output condition. Such a reduction is typically fromabout 1/6 to about 1/2, preferably about 1/4, the normal correctionpulse width. Each normal pulse can, by way of example, effect a cylinderhead movement at the rate of about 0.0005 to about 0.002 inches persecond of pulse length, although the first 0.05 to about 0.3 second of acorrection pulse is generally consumed in releasing a brake on thecompression ratio change motor, or in other electrical delays. Only thebalance of each pulse is actually devoted to compression ratio change.

Finally the 6-output line has another branch 116 which starts a timer102 operating. This timer is also connected by line 120 to a Not In DeadBand Detector 26 which causes the timer to be reset whenever a timingpulse from Timing Pulse Generator 44 shows that the test engine's knockintensity is not within the selected dead band. Connection by line 45 tothat Generator, and by lines 34 and 36 to Detectors 21 and 22, effectsuch operation.

Timer 102 can have a timing run of about 15 to about 30 seconds,preferably about 20 to 21 seconds, and has a stepping output at 103 tostep Sequencer 70 to its next output position when the timer times out.Also Detector 26 has an additional output line 121 connected to reset acounter 125 when it resets timer 102. Counter 125 counts pulsesdelivered by pulse generator 97 through line 126.

It is preferred that the timing run of timer 102 be long enough to showthat the knock intensity of the test engine is within the desired deadband during two to four successive up movements of the fuel bowl. Suchmovements of 0.025 inch each or even as little as 0.015 inch each, willbe enough to assure that the fuel-air ratio has become enriched to thepoint that it has passed through the maximum knock ratio and the knockintensity is no longer increasing with further enrichment. Indeed onlytwo upward steps of about 0.025 inch each are usually sufficient forthis purpose.

The test engine's knock intensity goes through a maximum or peak as thefuel-air ratio is increased, and when suitable increases are made to anexcessively lean ratio the knock intensity generally increases with eachfuel-air ratio increase until the ratio is very close to or at the peakratio. Each knock intensity increase will generally also cause acompression correction pulse that decreases the compression ratio of thetest engine and thus also decreases the knock intensity, keeping it inor just above the dead band. When two successive fuel-air ratioincreases of this type do not increase the knock intensity sufficientlyand the knock intensity remains below the upper limit of the dead band,the peak fuel-air ratio has been overshot slightly.

Timer 102 has a timing run that spans at least two successive fuel-airratio increases, so that the continued absence of a resetting signalfrom detector 26 during such a time span permits this timer to time outand generate a stepping signal at 103. This steps Sequencer 70 to its7-output position and stops further increases in the fuel-air ratio.Also the same absence of that resetting signal has permitted counter 125to count the number of fuel-air ratio increases that have been effectedwith the knock intensity in the dead band. This generally corresponds tothe overshoot of the fuel-air ratio increases.

In output stage 7, the sequencer effects a lowering of the fuel bowl tocompensate for the overshoot. The Compression Correction Pulse Generatoris again connected, through line 87, to generate decrease signals only.Also line 107 branched from line 87, reduces the duration of thecompression correction pulses that are generated, corresponding to thereduction effected by line 106 in sequencer output 6.

A pulse generator 137 similar to generator 97 is actuated by line 117branched from line 87, and generator 137 supplies its pulses to the downwindings 100 of the bowl motor. These pulses do not have to be spacedapart more than about 0.1 second, and are preferably just as long as thebowl-lifting pulses from generator 97 so that the up and down windingsof the bowl motor can be identical. If desired these bowl-down pulsescan be made slightly more or less effective than the bowl-up pulses, inorder to have the bowl-down compensation travel 10% or so more or lessthan the bowl-up travel to be compensated, and thus more accuratelycompensate for the overshoot of maximum knock ratio.

Line 129 delivers the bowl-down pulses to counter 125 and causes thatcounter to count down. When the count-down equals the count previouslyreached at the end of the bowl-up travel, counter 125 delivers astepping signal at an output 131. This steps Sequencer 70 to its8-output.

In its 8-output stage Sequencer 70 energizes the Compression CorrectionPulse Generator through line 88 and also energizes timer 102 throughline 118. This permits the test engine to run a little longer without afuel-air ratio change to make sure the engine is fully stabilized. Whenmaking Motor Octane ratings the knock intensity sometimes changes duringsuch stabilizing run and causes the generator of a compressioncorrection pulse. Such a pulse will cause detector 26 to reset timer102.

When timer 102 times out during the 8-output stage of Sequencer 70, itagain generates a stepping signal at 103, and this steps Sequencer 70 toits O-position where it enables the display of an octane number readoutcorresponding to the final position of the test engine's cylinder head.The octane number so displayed has been found highly reproducible andclosely correlated with octane numbers determined by the non-automaticmethod described in the ASTM Standards publication.

When conducting a Research Octane measurement the test engine does notneed further stabilization after the completion of stage 6 in thesequencing. Stages 7 and 8 can then be eliminated altogether, althoughstage 7 can be retained if it is desired that the fuel-air ratio at theend of the measurement be accurately fixed at the maximum knock ratio.

Suitable blocking provisions can be incorporated, for example to keepstep output 52 from actuating Sequencer 70 every time the knockintensity is within the selected dead band. Thus the reset line 52 canbe fed through an AND gate having a second input that is only energizedwhen Sequencer 70 is in its stages 1 or 2.

Some or all of the sequenced operating steps can be arranged to triggerthe next step without going through the sequencer. For instance the line52 can have a branch connected through an AND gate to start timer 95when that AND gate also receives an input from line 50. In such avariation sequencer stage 5 can be omitted.

Only about 3 minutes time is consumed by the octane determination, lessif the test engine at the start of the determination is operating at aknock intensity close to the selected dead band. When it also happens tobe operating with its carburetor bowl at a level close to that whichactuates the low bowl limit detector 23, the total time for an octanedetermination can be as little as 2 1/2 minutes.

The use of the 7th and 8th sequencer stage adds about 1/2 minute to adetermination.

As pointed out above the raising of the carburetor bowl is preferablyeffected in steps with a sufficient pause between steps to permit thetest engine to stabilize its operation at the particular level of thelast step. The first upward step of the bowl can be a large one, as muchas five to ten times the later steps inasmuch as the bowl is moving upfrom a position so low that even the fuel with the leanest maximum knockfuel-air ratio will require a substantial raising of the bowl.

Where the bowl lowering is to a very low level, as for example when thelowering is related to the lower limit of the dead band and the selecteddead band is very wide, the first bowl-up step can be made somewhatgreater. This step can in such situations be under the control of thedead band selector.

Instead of controlling fuel-air ratio by carburetor bowl height, othertechniques can be used. Indeed when making octane measurements ofgaseous fuels such as liquefied natural gas or other light hydrocarbons,such bowl height control cannot be used. The fuel and air can then besupplied to the engine intake through bleed valves operated by electricmotors that take the place of the carburetor bowl motor in thearrangement of FIG. 1.

Test engines generally respond more rapidly to mixture enrichment stepsthan to mixture leaning steps and so it is desirable to do the maximumknock fuel-air ratio determination in steps of mixture enrichment ratherthan steps of mixture leaning. By making the pauses between stepsseveral seconds longer, the maximum knock fuel-air ratio determinationcan be conducted with mixture-leaning steps and this adds about 1/2minute to the octane measurement sequence time.

The sequence time can be generally reduced by keeping the automaticengine compression correction in full operation between measurements. Inthis modification steps 1 and 2 of the measuring sequence commence assoon as the fuel to be measured is supplied to the engine so that adelay in operating a switch to bring in the remainder of the sequence,does not delay the completion of the sequence. When a series of octanemeasurements is made on a stream of fuel, as for example to monitor thestream, substantial time is saved by not having to begin a measurementsequence with stage 1. On the other hand when measurements are madeafter switching to new fuels, there is no need to wait for the engine tofirst stabilize on the new fuel inasmuch as such stabilization isgenerally complete by the time stage 2 terminates, and does not have tobe completed until stage 3 terminates.

Further time saving can be effected by having the automatic enginecompression control operating between octane measuring sequences, andwith the fuel mixture automatically controlled to be on the lean side ofthe maximum knock ratio. This is done by modifying the stand-byoperation, as by either arbitrarily returning the fuel bowl to a levelfrom which essentially all fuels are supplied a little lean, or as byproviding an automatic bowl control that cooperates with the automaticcompression correction control to automatically lower the bowl after acompression correction and to repeat the bowl-down movement if thelowering results in an automatic decrease in compression. This canreduce the amount of bowl lowering needed in stage 3 of the automaticoctane measuring sequence, and save time this way.

To guard against an excessively low pre-positioning of the bowl, thisautomatic bowl pre-positioning control can also be arranged to raise thebowl when an automatic compression-increasing signal is produced after abowl-down step, and to repeat the upward bowl movement so long as theprevious bowl-up movement results in a compression-decrease signal.

A little reduction in sequence time can also be effected by moving thecompression correction stage 4 from its order between stages 3 and 5,and place it instead between stages 5 and 6. The compression ratioadjustment will still bring the compression ratio to the dead bandbefore the intermittent small upward steps of the bowl in stage 6, butthe adjustment will not have to be as large as needed when the bowl hasnot yet made its long first upward climb in stage 5. Less compressionratio adjustment time will accordingly be consumed.

According to another variation, the sequencer can be connected to bringthe carburetor bowl to a predetermined low level, after an octane numberdetermination is completed, so that the bowl is ready to immediatelybegin its upward steps for the next octane number determination. Thepredetermined low level can be selected as the lowest level reached bythe bowl with all fuels, when it goes through the octane determiningsequence illustrated in FIG. 1. This low bowl position will accordinglybe at or below the level needed to start the stepwise upward movements,regardless of the fuel to be tested, and a test sequence is initiatedwithout the delay involved in the bowl lowering.

In the last-mentioned variation automatic compression ratio adjustmentcan also be kept in operation to bring the test engine knock intensitywithin the dead band while the bowl is in its lowest or base positionand before a test sequence is started. With some fuels such low bowlposition may be too low for the knock intensity to reach the dead band,and the sequencer can be modified to then automatically raise the bowlenough for the knock intensity to reach the dead band. The equipmentthus is made ready to start and very rapidly complete theoctane-determining sequence.

The base position of the carburetor bowl in the foregoing variations canbe that at which stage 5 of FIG. 1 commences, or at which stage 6commences.

The position of the test engine's cylinder head with respect to itscrankcase should be accurately measured in order to give accurate octanereadouts. In accordance with the present invention it has been foundhighly effective to use a resistance type potentiometer, preferably witha sliding tap, as illustrated for example in FIGS. 3 and 4. Theresistance element of the potentiometer is preferably of very uniformcharacteristics such as described in U.S. Pat. No. 4,036,786 and shouldhave a linearity within ±0.1%.

FIGS. 3 and 4 show an upper block 201 secured by bolts 203 to thecylinder head 210 of the test engine, with a lower block 202 secured tothe crankcase 211 by mounting bolts 204. Both blocks are preferably madeof thermal insulation such as molded plastics, delrin (polyformaldehyde)being very effective. Grooved aluminum heat dissipation plates 206,207are illustrated as interposed between the blocks and the engine parts toreduce the transfer of heat from the engine to the blocks.

In a pocket 208 formed on one side of block 202, potentiometer 220 issecurely fixed as by a mounting strap that is not shown. The slidershaft 221 of the potentiometer projects upwardly through an aperture ina flange 224 at the top of block 202. An O-ring 225 is fitted in agroove in the aperture wall and engages shaft 221 to act as a dust seal.The shaft is also urged upwardly by a cross-bar 230 of splitconstruction clamped around the shaft and also clamped around two spacedguide pins 231, 232. These pins project downwardly into sockets 233, 234in block 202 while coil springs 241, 242 surround the respective pinsand are compressed between the bottoms of the sockets and the cross-bar.

The top of shaft 221 is thus urged against an adjustable engagementplate 244 carried by a threaded rod 245 threadedly engaged in an upperwall 205 of block 201. Adjustment of the position of plate 244 iseffected by means of a screw-driver slot 246 in the top end of the rod245, and a locking jam nut 247 can be used to lock the adjustment.

An upward force of about 1/2 pound urging shaft 221 against plate 244holds them in firm contact notwithstanding the vibrations generated bythe test engine as it operates, and causes the shaft to accuratelyfollow all up and down movements of the cylinder head with respect tothe crankcase. Leads connected to the three potentiometer terminalssupply the electrical signals corresponding to the shaft position.

The blocks 201, 202 can also be fitted with one or more limit switchesresponsive to the travel limits of the cylinder head. As shownvertically-extending tabs 251, 252 have their upper ends secured toupper block 201 and a vertically-extending slot 253 in their lowerportion. Received in this slot is a sensing arm 255 of a limit switch257, 259 carried by the lower block 202. The slot 253 and arm 255 are sorelated that limit switch 257 is tripped when the cylinder head movesdownwardly far enough to increase the engine's compression ratio to thepoint at which operation of the engine becomes risky. The tripping ofthe switch can be arranged to shut down the engine and/or generate awarning signal.

The second tab-and-switch assembly can be used to correspondingly reactwhen the compression ratio of the test engine is at its low limit, orslot 253 can be dimensioned so that its lower end trips switch 259 intowarning position at that limit.

FIGS. 3A and 4A illustrate a modified attachment arrangement forcoupling the cylinder height sensor (potentiometer 220) to a testengine. This arrangement can utilize the same mounting blocks 201, 202held in place the same way as in FIGS. 3 and 4, but without the sockets233, 234.

In place of cross-bar 230, the modified arrangement has magnetic collar330 shrunk or threadedly secured on the upper end of slider shaft 221.This collar is magnetically attracted to a magnetic insert 344 fastenedto the lower end of adjustment rod 245, the insert taking the place ofengagement plate 244.

One or both of the collar 330 and insert 344 is permanently magnetizedso that these two members are attracted to each other and held incontact with sufficient force to overcome the weight of slider shaft aswell as the frictional resistance offered by wiper seal 225 and by theengagement of the slider shaft with the potentiometer winding. In thisarrangement slider shaft faithfully follows all up and down movements ofthe engine cylinder 210 with respect to the crankcase 211,notwithstanding the vibrations and knocking of the test engine as itoperates. Also the smaller number of moving parts and the absence ofsprings from the modified arrangement leaves less chance formisoperation.

While it is generally desirable to use brass or stainless steel of lowmagnetic permeability for metal members such as the slider shaft 221 andthe threaded rod 245, one or both of them can alternatively be made ofhigh magnetic permeability metal or high coercive force metal. In such avariation the insert 344 or collar 330 or both are not needed and theupper end of the slider shaft can directly engage the lower end of thethreaded rod.

FIG. 4A also shows a single limit switch 357 operated by two controltabs 351, 352. This switch has an arm 355 that can take three positions,a central one, as illustrated, which it normally occupies, an upper oneinto which it is tripped by upward movement of tab 352, and a lower oneinto which it is tripped by downward movement of tab 351. In both ofthese tripped positions the switch gives warning of improper engineoperation, or shuts the engine down.

Another feature of the present invention is that the octane number canbe displayed as such rather than as a cylinder height position, and canhave a built-in barometric pressure correction so that no computation isneeded. FIG. 2 shows one very effective arrangement to this end.

FIG. 2 shows a barometric pressure transducer 300 connected to operate apotentiometer 302 from which output leads 304 are connected to an analogdriver 306 that delivers at 308 an analog voltage corresponding to theambient atmospheric pressure. A cylinder head height transducer 312,which can be the transducer of FIGS. 3 and 4, supplies its signalthrough line 314 to another analog driver 316 which delivers at 318 ananalog voltage corresponding to the cylinder head height.

Both analog voltages are supplied to a scaling and summing amplifier 320which converts them to values in appropriate scales of values suitablefor combining to make the barometric adjustments described in Tables 4and 15 (pages 31 and 62) of the above ASTM publication. Amplifier 320 isconnected to sum the scaled values in two different ways, in accordancewith the Research Octane barometric correction (Table 4) or the MotorOctane barometric correction (Table 15), and a settable selector 322determines which way the correction is applied.

The corrected signals are then supplied by line 324 to ananalog-to-digital converter 326 which delivers corresponding 10-bitbinary coded decimal signals through driver 328 to a Research memorycomparator 331, a Motor memory comparator 332, and a logic indicator333. Comparator 331 contains a memory in which is stored the octanenumber values for each 10-bit signal that can be obtained by theResearch octane determining method, and comparator 332 a memory storingthe octane number values for each 10-bit Motor octane signal. Indicator333 is not needed; it merely provides an L.E.D. display of the 10-bitsignals so that this can be checked in the event misoperation issuspected. Logic indicator 20 of FIG. 1 serves the same purpose. Amemory bank of only about 4000 words or 16,000 bits is adequate for eachcomparator.

A binary-to-7-segment driver 340 has a selector 342 coupled withselector 322 and arranged to receive the output of comparator 331 or 332and to deliver through its own output 344 a 7-segment signal to a7-segment readout unit 348. An enable line 350 energized by the O-outputof Sequencer 70 of FIG. 1, illuminates or exposes the 7-segment readout,and can also sound an audible signal such as a gong to announce thecompletion of a test sequence. The octane number can also be supplied byoutput 344 to a printer for automatic recording, and/or to a computerfor storage and subsequent reference. It is sometimes helpful to makeautomatic records of entire test sequences on a time scale showing thecompression ratio values at various stages of each sequence, and thus beable to check back and verify that there was no equipment misoperationand the final octane number readout is a valid test result.

If desired the apparatus of FIG. 2 can also be provided with a separatereadout 325 to show compression ratio of the test engine, with orwithout the barometric correction. Such a readout is obtained byrescaling the output of amplifier 320 or the output of driver 316.

The above-described apparatus can be fitted to a test engine withoutinterfering with the manual operation of the engine. Thus when theapparatus is in stand-by condition the compression ratio of the testengine can be changed by operating the manual change control 60. Testengines usually have several carburetor bowls that can be selectivelyused to supply fuel and only one of the bowls need be equipped with theautomatically controlled bowl motor. In addition the bowl motor can alsobe supplied with a manual control so that its bowl can be raised orlowered at will.

A stand-by switch can also be provided and connected to supply amomentary reset signal to line 74 and thus shift the apparatus tostand-by operation in the event it is operating in the automatic octanedetermining mode.

The various electrical components of the apparatus of the presentinvention can use standard off-the-shelf components connected in amanner that is clear from the above description. The CompressionCorrection Pulse Generator 28 is illustrated in greater detail in FIG.5, although other constructions can be utilized.

FIG. 5 shows the Compression Correction Pulse Generator within thedash-line outline 28, and also shows timing pulse generator 44 connectedto it. The heart of generator 28 is a standard pre-settable counter 140in integrated circuit form designated CD 40103, having its pins 4, 5, 6,7, 10, 11, 12 and 13 connected to receive the respective bit signals ofthe 8-bit knock intensity error generator 30. Pin 9 is a jamming orlocking connection that receives the timing pulses from the timer 44,each timing pulse causing the counter 140 to fix or lock in the errorbit count at that instant. Pin 14 of the counter delivers an outputsignal whenever an error count of any magnitude (not zero) is thusfixed.

Timing pulses are also delivered by line 45 to pin 3 of counter 140, andthese pulses illustrated at 142 temporarily block the counting functionof the counter for the duration of each short timing pulse. When notlocked, the counting function of counter 140 is actuated by supplying toits pin 1 the counting pulses delivered by an oscillator 145 shown asintegrated circuit CD 4098. Each such counting pulse counts down onefrom the error signal that was locked in counter 140 when its pin 9 wasactivated, but this count-down does not commence until after thecompletion of the short timing pulse that blocked the counting. Thecount lock-in does not require continued activation of pin 9, but isreduced by the counting action, and whether or not reduced to zero isswitched to a new lock-in or fix when the next timing pulses reaches pin9. The new lock-in corresponds to the bit error signal at thecommencement of that timing pulse.

Oscillator 145 is arranged for oscillation to generate square wavecounting pulses at two different periods such as 0.04 and 0.01 seconds,respectively. These counting pulses are generated at pins 10 and 12 ofoscillator 145 when its pin 4 is activated, and the counting pulseperiod is determined by the presence or absence of activation in line146. Such activation is independently effected by lines 106 and 107(FIG. 1). When neither 106 nor 107 is activated, oscillator 145generates its counting pulses as the longer period, so that the errorsignal count-down in counter 140 takes a relatively long time. Thelargest error signals can be such that this slow count-down takes up allthe time between timing pulses 142, or even requires more time.

Pin 14 of counter 140 remains activated during the entire count-down,and only becomes deactivated when the count-down reaches zero.Activation at this pin delivers a signal through an OR gate 148 whichcan be type CD 4071, and lead 149, to AND gates 151, 152 and 153. Asimilar timing pulse signal is delivered from line 145 through the ORgate to the same AND gates.

AND gate 153 which can be type CD 4081, is shown as having two inputs,one from line 45 and the other from output pin 9 of oscillator 145. Withthat oscillator connected as shown, this output pin is energized onceeach oscillation period, and energization delivered by the OR gate tolead 149 will then cause the square wave counting pulses to be generatedat output pins 10 and 12 of the oscillator. Thus the initiation of atiming pulse 142 will initiate the counting pulses and they willcontinue as long as any error locked into counter 140 is not fullycounted down. For the duration of the initiating timing pulse thecounting pulses are ineffective to count down the error, because anyreduction in the locked-in error signal is blocked by the activation ofpin 3 in the counter.

At the termination of the initiating pulse the count-down becomeseffective and if it reaches zero before the next timing pulse, AND gate153 stops passing a signal so that the counting pulses stop. If thecount-down does not reach zero by the time the next timing pulsearrives, the counting pulses continue but become ineffective by theblocking action of the timing pulse at pin 3 of the counter and at thesame time the error signal being then received by the counter from theerror bits is locked in the counter. Upon the termination of the newtiming pulse, count-down of the newly locked-in error signal willproceed unless the newly locked-in signal is zero.

The energization delivered to lead 149 is a continuous motor-controlpulse initiated by the initiation of a timing pulse 142 and terminatedwhen the error signal is counted down to zero, or when the timing pulseterminated if the error signal is then zero. This motor-control pulse isdelivered to AND gates 151 and 152 and when appropriate passed to theproper winding of the compression ratio control motor on the testengine. Such passage is determined by the condition of the knockintensity signal. AND gate 151, which can be a duplicate of AND gate153, has two input leads one of which, 156, is connected to high output34 (FIG. 1) of the above-dead-band detector. The other input lead ofgate 151 is lead 149 and motor-control pulses are accordingly passed tocompression decrease output lead 161 of gate 151 only when the knockintensity is above the selected dead-band.

On the other hand such motor-control pulses are only passed tocompression increase output 162 of AND gate 152 when the knock intensityis below the dead-band and the compression is to be increased. To thisend AND gate 152 is a four-input gate, type CD 4082, one of the inputs,157, being connected to low output 36 of below-dead-band-detector 22.Another input 158 is connected through inverter 168 to line 146, and athird input 159 through invertor 169 to line 83 (FIG. 1). The fourthinput is from lead 149.

When neither lead 146 nor lead 83 is energized, both inputs 158 and 159are energized so that compression ratio increases are controlled in amanner correllative to the manner compression ratio decreases arecontrolled. However energizing line 83 (at step 3 of sequencer 70)causes lead 159 to become de-energized so that compression increasesignals are blocked. Also when line 146 is energized lead 158 becomesde-energized and again compression increase signals are blocked. Aspointed out above, energizing lead 146 also shifts the oscillator 145 toits short-period oscillation so that error count-down becomes muchfaster and compression control pulses much shorter. It is preferred thatthese short pulses be no longer than about 3 seconds when the errorsignal is at its maximum and that apart from the fraction of a secondneeded for the compression control signal to prepare the compressionchange motor for actually increasing the compression ratio, thecompression control signal vary in duration with the magnitude of thelocked-in error, the minimum control signal being sufficient to move thetest engine cylinder about 0.3 mil or increase the compression ratioabout 1/2 a compression ratio number. These numbers indicate cylinderpositions and can range from 172 to 1195.

Inventors 168,169 can both be type CD 4049, and timing pulse generator44 can be an oscillator type CD 4098, like oscillator 145.

In many cases the barometric connection arrangement of FIG. 2 can besimplified by constructing it with only a Research Octane correction oronly a Motor Octane correction, and eliminating switches 322, 342. Bothconnections can be used with any Octane Test engine where an extremelyversatile test engine installation is desired, but it is generally tooawkward to make the many manual adjustments needed to convert a testengine set-up from Research Octane determining operation to Motor Octanedetermining operation. To avoid such awkwardness separate test enginesare frequently used, one permanently set up for Research Octanedeterminations, and the other for Motor Octane determination. Eachset-up can have its own automatic controller of FIG. 1, but needs onlyone type of barometric correction and one of the memories 331, 332.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. An all-electronic controller for responding toerror signals, said controller including(a) a receiving unit forreceiving and periodically locking in a digital error signal, (b) acounting unit connected to count down the error signal after it islocked in, (c) a control circuit connected to deliver one output signalduring the error count-down and to deliver another output signal whenthe error count-down reduces the locked-in error to zero, and (d) shiftmeans connected for external actuation to shift the count-down from ahigh count rate to a low count rate,the receiving unit is connected toan octane test engine knock signal output, and the control circuit isconnected to deliver its output signals to the compression ratio changeactuator of the test engine.
 2. The combination of claim 1 in which thecontroller also has an externally-actuated inhibitor input connected toinhibit the delivery of one of the control output signalsnotwithstanding an error signal calling for such output.